ALTERED ALPHA(1)-ADRENOCEPTOR DENSITY AND ALPHA(1A) ALPHA(1B) RATIO IN RAT HEARTS AFTER PROPRANOLOL TREATMENT/

After rats were treated with propranolol (50 mg . kg(-1), bid, ip) for 7 d, the density of alpha(1)-adrenoceptors in the rat myocardial cell membranes increased from 137+/-25 to 178+/-30 fmol/mg protein determi ned by receptor radioligand assay. Whereas the K-D value was not signi ficantly changed, the relative proportion of alpha(1A)-adrenoceptor su btype increased from 19+/-6 to 31+/-8%. The affinities of two subtypes to 5-methylurapidil were not obviously changed after pyopranolol trea tment. It was suggested that alpha(1A)-subtype was more important in a lpha(1)-receptor mediated alterations after beta-adrenoceptor blockade .